Heavy air reaching requires keeping the boat on plane, anticipating gusts, and avoiding capsizing. The controls are much less important in these conditions, sailing fast is key since it reduces the load on the rig.
The boat will easily get up on plane so the outhaul can be tighter than in medium wind. The upwind outhaul setting usually works pretty well for heavy air reaches although the outhaul can be eased 4-6 inches. The higher the wind the more power in the sail, so less draft in the sail is needed. The Cunningham should be off unless sailing on a tight reach. The vang setting on a heavy air reach is a compromise between the boom skipping on the water and twist in the sail. When overpowered ease the vang to allow the boom to rise spill excess power from the top of the sail.
On a heavy air reach we want to attain maximum vmg. A slightly loosened kicker can help with steering by reducing weather helm. Constantly trim the boat and maintain a constant heel. This is accomplished by simultaneously moving your body and sheeting the main. Remember that the faster the boat goes the less pressure is on the rig, so sailing faster makes it easier to keep the boat stable and in control. When you reach a gybe mark keep the boat moving as fast as possible, again to reduce the pressure in the sail. It’s important to fully commit to the gybe, any hesitation will cause a capsize. Avoiding a capsize in a race is important, in extreme conditions simply avoiding a capsize can be the boost needed to reach the podium.